Industrial application of thermal methods of oil recovery improvement implies prior simulation of heat and mass processes in reservoirs and wellbores as well as evaluation of thermal regime of downhole equipment. This fact raises the importance of problems concerned with the study of heat transfer in porous media (rock samples) that are composed of generally non-uniform solid skeleton and pores filled with one or several fluids—gases or liquids.
Thermal conductivity (TC) is normally measured in the laboratory on core, crushed samples, or well cuttings using one of two techniques: divided bar or needle probe (see, for example, H.-D. Vosteen, R. Schellschmidt “Influence of temperature on thermal conductivity, thermal capacity and thermal diffusivity for different types of rock”, Physics and Chemistry of the Earth, 28 (2003), 499-509).
All these methods provides for thermal treatment of the samples followed by measurements. But heating is not desirable for liquid-filled samples since at heating the liquid partly vaporizes and forms gas locks inside the pore space which results in thermal conductivity error.
Physical models that were developed for effective TC calculation include three parameters: solid phase TC, saturating phase TC and microstructure of porous space. Ones the detailed internal microstructure of rock samples is obtained it become possible to determine the effective TC solving the thermal conductivity equation numerically (S. V. Patankar, ‘Numerical Heat Transfer and Fluid Flow’, Taylor&Francis, 1980, pp. 59-61). The direct numerical solution of thermal conductivity equation can be extraordinarily challenging when all the details of the complex 3D rock microstructure are accounted for. Sometimes it is impossible to apply this method because of significant expenses of computing time spent to perform calculations and incredibly expensive cost of computer resources needed for such simulations carrying out.